Dental Cements
Introduction
Dental cements are a classification of dental materials that are continually used in dentistry. The American Dental Association and the International Standards Organization (ISO) have teamed up to classify dental cements according to their properties and their intended uses in dentistry.
Classification of Cements
* Type I: Luting agents that include permanent and temporary cements.
* Type II: Restorative applications.
* Type III: Liner or base applications.
Luting Agent
* A material that acts as an adhesive to hold together the casting to the tooth structure. Luting agents are designed to be either permanent or temporary.
Permanent Cement
* For the long‑term cementation of cast restorations such as inlays, crowns, bridges, laminate veneers, and orthodontic fixed appliances.
Temporary Cement
* Temporary cements are used when the restoration will have to be removed. Most commonly, temporary cement is selected for the placement of provisional coverage.
Variables Affecting Cements
* Mixing time
o Make sure to follow the manufacture’s directions for the mixing time, working time, and delivery time.
* Humidity
o If the clinical area is warm or humid, premature exposure of the cement to these environments can create a loss of water from the liquid or an addition of moisture to the powder.
* Powder to liquid ratio
o Incorporating too much or too little powder will alter the consistency.
* Temperature
o Some types of cements put off an exothermic reaction.
Mixing Dental Cements
* Before mixing, read and carefully follow the manufacturer's directions for the brand being mixed.
* Determine the use and then measure the powder and liquid according to the manufacturer's instructions.
* Place the powder toward one end of the glass slab or paper pad and the liquid toward the opposite end (the space between allows room for mixing).
* Divide the powder into increments.
* When increment sizes vary, the smaller increments are used first.
* Incorporate each powder increment into the liquid and then mix thoroughly.
Types of Cements
* Zinc-oxide eugenol
* Zinc phosphate
* Polycarboxylate
* Glass ionomer
* Composite resin
Zinc Oxide Eugenol
* Chemical Makeup
o Liquid: Eugenol, H2O, acetic acid, zinc acetate, and calcium chloride.
o Powder: Zinc oxide, magnesium oxide, and silica.
Types of Zinc-Oxide Eugenol
* Type I
o Lacks strength and long‑term durability and is used for temporary cementation of provisional coverage.
* Type II
o Has reinforcing agents added and is used for the permanent cementation of cast restorations or appliances.
Supply of Zinc-Oxide Eugenol
* Liquid/Powder
o Mixed on an oil‑resistant paper pad.
o Mixing time ranges from 30 to 60 seconds.
o Setting time in the mouth ranges from 3 to 5 minutes.
* Paste
o Supplied as a two‑paste system as temporary cement.
o Pastes are dispensed in equal lengths on a paper pad and mixed.
Zinc Phosphate
* Chemical Makeup
o Liquid: Phosphoric acid, aluminum phosphate, and water.
o Powder: Zinc oxide, magnesium oxide, and silica.
Types of Zinc Phosphate
* Type I (fine grain)
o Used for the permanent cementation of cast restorations such as crowns, inlays, onlays, and bridges. This material creates the very thin film layer that is necessary for accurate seating of castings.
* Type II (medium grain)
o Recommended for use as an insulating base for deep cavity preparations.
Supply of Zinc Phosphate
* Powder/liquid
o Powder is divided into increments that vary in size.
o It is critical that the powder be added to the liquid in very small increments.
o Cement must be spatulated slowly over a wide area of a cool, dry, thick glass slab to dissipate the heat.
Polycarboxylate Cements
* Chemical Makeup
o Liquid: Polyacrylic acid, itaconic acid, maleic acid, tartaric acid, and water
o Powder: Zinc oxide
Use of Polycarboxylate
* Used as a permanent cement for cast restorations, stainless steel crowns, and orthodontic bands.
* Used as a nonirritating base under both composite or amalgam restorations.
* Used as an intermediate restoration.
Supply of Polycarboxylate
* Powder/liquid
o Liquid may be measured by using either the plastic squeeze bottle or the calibrated syringe‑type liquid dispenser.
o Liquid has a limited shelf life because it thickens as its water evaporates.
o Mixed on a nonabsorbent paper pad.
Glass Ionomer
* Chemical Makeup
o Liquid: Itaconic acid, tartaric acid, maleic acid, and water.
o Powder: Zinc oxide, aluminum oxide, and calcium.
Types of Glass Ionomer
* Type I
o For the cementation of metal restorations and direct‑bonded orthodontic brackets.
* Type II
o Designed for restoring areas of erosion near the gingiva.
* Type III
o Used as liners and dentin bonding agents.
Benefits of Glass Ionomer
* Powder is an acid‑soluble calcium. The slow release of fluoride from this powder aids in inhibiting recurrent decay.
* Causes less trauma or shock to the pulp than many other types of cements.
* Low solubility in the mouth.
* Adheres to a slightly moist tooth surface.
* Has a very thin film thickness, which is excellent for seating ease.
Supply of Glass Ionomer
* Powder/liquid
o Mixed manually on a paper pad or a cool, dry glass slab.
o Glass slab increases the working time of the cement.
* Premeasured capsules
o Triturated and expressed through a dispenser.
Composite Resin
* Chemical Makeup
o Physical properties are comparable to those of composite resins.
o Low film thickness.
o Insoluble in the mouth..
Uses of Composite Resin
* Cementation of ceramic or resin inlays and onlays.
* Cementation of ceramic veneers.
* Cementation of orthodontic bands.
* Direct bonding of orthodontic brackets.
* Cementation of all metal castings.
Supply of Composite Resin
* Powder and liquid mix
* Syringe-type applicator
* Base and catalyst
* Light cure/dual cure system
o Recommended portions of either application are dispensed onto a paper pad and mixed rapidly with a spatula.
Cement Removal
* Operator preparedness and knowledge
o Instruments selected for the procedure: Explorer, mouth mirror, black spoon.
o Use of a fulcrum.
o Use of dental floss in and around the embrasure areas.
Copyright 2003, Elsevier Science (USA).
All rights reserved. No part of this product may be reproduced or transmitted in any form or by any means, electronic or mechanical, including input into or storage in any information system, without permission in writing from the publisher.
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